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Geoheritage of Grand Canyon National Park’s Rock Record

Photo of a raft floating on a river in a steep-sided canyon.
Boating down the Colorado River below Havasu Creek in Grand Canyon National Park.

NPS photo by Mark Lellouch.

Introduction

With one of the clearest exposures of the rock record and a long, diverse geologic history, Grand Canyon NP is an ideal place to gain a sense of geologic (or deep) time, especially given the great antiquity of those rocks. Rocks exposed in Grand Canyon’s walls record approximately one third of the planet’s history, from the Precambrian (Proterozoic Eon) to the Permian Period of the Paleozoic Era, and contain important information about the evolution and history of life (Santucci and Tweet 2020). These strata, along with younger deposits within the canyon, illustrate much of the tectonics, evolution, and geologic history of the western United States.

Photo showing grand canyon cliffs, mesas, and rock layers.

Figure 2. Earth history revealed: Vishnu Basement Rocks at the canyon’s bottom are nearly 2 billion years old. The youngest of the Grand Canyon strata on the South Rim skyline was deposited about 270 million years ago. The canyon landscape has been carved in only the past 5–6 million years
Chappell Aerial Photo courtesy of NPS.

Highlights of Grand Canyon’s Geologic Ages

  • The oldest basement rocks exposed in Grand Canyon (Figure 2) are ancient; 1,840 million years old.

  • The Kaibab Formation, the youngest of Grand Canyon’s strata, holds up both the North and South rims. The Kaibab is 270 million years old, and was deposited prior to the age of the dinosaurs.

Photo steep rocky cliffs.
Figure 3. Lava flowed into the western Grand Canyon during the past 600,000 years. This cascade is called Devils Slide. The age of these younger surficial deposits help researchers understand modern landscape evolution.

Chappell aerial photo courtesy of NPS.

  • Today’s canyon is geologically quite young, having been carved in the past 5–6 million years.

  • Younger deposits within Grand Canyon, including Ice Age fossils in caves, 1,000-year-old lava flows that cascaded into the western canyon (Figure 3), recently-deposited debris flows, and river sediments that record oscillating climates and human influences, bring Grand Canyon’s geologic record to the present.

The geology of Grand Canyon and the long time frames encoded by its rocks can be hard to comprehend.

The first geologists who explored and studied Grand Canyon included John Strong Newberry, who was part of the Lieutenant Joseph Christmas Ives expedition of 1857–1858, and John Wesley Powell, who led the famous 1869 expedition down the Colorado River. They classified and correlated the canyon’s rock units based on fossils and the geologic knowledge that was available at the time. Early studies of Grand Canyon geology could only describe the age of Grand Canyon rocks in the broadest of parameters. With the later development and refinement of techniques that determine the numeric ages of rocks, geologists developed the ability to know the ages of rocks exposed in Grand Canyon with greater accuracy and precision. Advancements in geologic dating techniques are part of a renaissance of geologic research in the canyon that accelerated in the late 1990s.

Park Significance

Grand Canyon NP was established in 1919 and has been enlarged to encompass most of the physiographic Grand Canyon in northern Arizona (Figure 6). It is one of the most famous and highly visited parks in the National Park System, attracting visitors for many reasons. It has diverse animals and plants in ecosystems that span desert to mountain life zones. Its human history traces cultures back to more than 10,000 years ago. Its beauty has inspired artists and poets. Its societal importance involves all of these aspects and more. Behind it all, geology is its most prominent and important resource.

Park map showing river and park boundary.
Figure 6. Grand Canyon National Park and associated federal lands in northern Arizona now include nearly the entire Grand Canyon from Lake Powell to Lake Mead.

NPS image.

Grand Canyon is one of the planet’s most iconic geologic landscapes. The purpose of Grand Canyon National Park is to preserve and protect its natural and cultural resources, and the ecological and physical processes of Grand Canyon along with its scenic, aesthetic, and scientific values for the benefit and enjoyment of the public (NPS 2017). Geology has always been recognized as central to the canyon’s significance, from its description as “the greatest eroded canyon in the United States” (1908 proclamation of Grand Canyon National Monument by Theodore Roosevelt) to its designation as a UNESCO World Heritage site for being “among the Earth’s greatest ongoing geological spectacles.”

Grand Canyon is probably the single location on the planet that provides the best opportunities for both researchers and students to learn about geology. The canyon remains an important field laboratory for active researchers. It also provides great opportunities for informal and formal science education via promotion of national and global geoscience literacy, both on site and remote learning.

All of the park’s natural and cultural resources are intertwined with its geology and geologic history. Therefore, telling geologic time and relating human and geologic timescales are important parts of the stories of Grand Canyon National Park.
Geologic time also provides the framework for understanding much more than bedrock geology, such as water supply for the park’s 6.5 million annual visitors, the waxing and waning of flow in the Colorado River, the history and future of mining in the Grand Canyon region, analysis of geologic hazards, and the nature and interaction of Grand Canyon’s ecosystems under changing climate regimes.

Understanding Geologic Time

A full understanding of geologic time encompasses diverse geologic topics including plate tectonics, stratigraphy, historical geology, paleontology, and geomorphology. Advances in understanding the history of our planet often begin in a well-exposed and well-known location like Grand Canyon, but quickly extend to include other areas. Grand Canyon is connected to other national parks on the Colorado Plateau, such as Arches, Bryce Canyon, and Zion that share an overall geologic history, and has a common erosional history with other parks located along the Colorado River and its tributaries, such as Black Canyon of the Gunnison National Park, Colorado National Monument, and Lake Mead National Recreation Area.

On an even broader scale, Grand Canyon’s rock record provides important information about the tectonic history of North America as it contains data about the formation of new continental crust early in its history and has been influenced by current tectonic environments. Grand Canyon is one of many park areas that has had an outsized role in the development of the science of geology in North America and an important locale for increasing geoscience literacy in the public. Many such park areas have been formed by dramatic events in planet’s history

Significance of Grand Canyon’s Rock Record

  • Grand Canyon NP’s rock record has global significance and provides important information about the geologic history of the southwestern portion of the North American continent.

  • The Vishnu Basement Rocks provide one of the best views into the early history of North America in the Colorado Plateau region where outcrops of basement rocks are few. The history of the Vishnu Basement Rocks can be compared to rocks of similar age exposed in Colorado National Monument, Black Canyon of the Gunnison National Park, Rocky Mountain National Park, and elsewhere in and around the Colorado Plateau. Together, these exposures provide a synthesis of the early history of North America that can then be compared to similar rocks on other continents) to reconstruct global plate configurations.

  • The Grand Canyon Supergroup provides one of the best records in North America of the Proterozoic Eon from 1.25 to 0.7 billion years. Similar rocks of this age exist only in a few places like at Death Valley NP, central Arizona, and the Uinta Mountains in northern Utah. Hence, the Grand Canyon record anchors the scientific understanding of the geologic history of this time period).

  • Units in the Layered Paleozoic Rocks are also proving to be of global importance, especially for understanding the Cambrian Period. Together with the mostly younger rocks exposed in the rest of the Colorado Plateau, Grand Canyon provides one of the world’s best sedimentary rock records for studying the evolution of life.

Learn More

Tiny image of the cover of a report titled Telling Time at Grand Canyon National Park.

To learn more about the age of Grand Canyon’s rocks, please see:

Karlstrom, K., L. Crossey, A. Mathis, and C. Bowman. 2021. Telling time at Grand Canyon National Park: 2020 update. Natural Resource Report NPS/GRCA/NRR—2021/2246. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/nrr-2285173. [IRMA Portal]

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Last updated: January 30, 2024